Molded glass article



H. P. HOOD 2,466,849

MOLDED GLAS S ARTICLE April 12, 1949. 7

Filed Jan. 3, 1944 3 Sheets-Sheet l Sin i-A1 0 April 12, 1949. oop2,466,849

MOLDED GLASS ARTICLE Filed Jan. 3, 1944 V v 5 Sheets-Sheet 2 WWW QttumepApril 12,1949. H. P. HOOD 2,466,849

MOLDED GLASS ARTICLE Filed Jan. 5, 19.44 3 Sheets-Sheet 5 Zinhentorflame/so 14 000 Patented Apr. 12, 1949 MOLDED GLASS ARTICLE Harrison P.Hood, Corning, N. Y., asslg'nor to CornlngGlass Works, Corning, N. "L, acorporation of New York Application January 3, 1944, Serial No. 516,794

4 Claims. (01. 106-54) This invention relates to the molding or shapingof glass articles and particularly to the molding of intricate glassshapes the production of which has heretofore been impossible becausethe physical properties of glass place certain limitations on the priormethods. Ordinary shaping methods for the molding of molten glass arenot adapted tor making some articles, for example, articles ofsubstantial thickness having reticulated designs and small'periorations, because any implement employed for making fineperforations heat. crystallized and became worthless whe I in moltenglass becomes red-hot and either adheres to the glass or burned off.These difficulties might be avoided if the glass could be machined ormolded while cold, but glass per se is not machinable and although itcan be sawed and drilled by special devices, such methods would be verycostly and would not suflice'for fine delicate patterns.

The primary object of this invention is to make perforated orreticulated glass articles. v Another object is to .form such shapedarticles by vpowdering a glass, molding the powder under pressure andsintering the compacted powder to a yitreous non-porous body.

A further object is to provide glass bodies comprising vitreous,non-porous, sintered, powdered glass.

Still another object is to provide glass compositions which areparticularly suitable for powdering, compacting and sintering and whichwill not devitrify nor undergo substantial change in expansioncoeflicient when so treated. I

I have discovered that many shapes and sizes of glass articles, whichcould not heretofore be produced, can now be made by such methods.provided the compositions employed fall within certain limits. Thesecompositions may be defined generally as alkali metal ltlorosilicatescomprising from 60% to 83% Si'Oz, from 0 to 6% A1203, from 1% to 21% R(alkali metal oxide) and from 8% to 39% .3203, the ratio 'RzO/BzOs.being less than 1.1. p

Several difficulties had to be overcome in the adaptation of glass tosuch methods of procedure. The most serious difllculty consisted in thetendency of the powdered glass to devitrify during firing. Glasses,which in massive form were known -to be highly resistant todevitriflcationjby pulverized and heated at sintering temperatures. Theexpansion coefiicient of the glass, l'iith'erto considered to be asubstantially :unchangeable characteristic of glass, was also alteredand in extreme cases increased more than threefold. Thus it was apparentthat fine subdivision of glasses which are normally stable to heatresults in serious loss of stability and change expansion coeflicientwhen heated. This fact was .not hither-to known or appreciated.

For determining the suitability of any "composition for my purpose, thefollowing procedure was used. The glass was pulverized by beingcomprising about 015% by weight of cellulose 'nitrat'e' dissolved insuflicient amyl acetate to make the powder coherent when pressed but notsticky. The batch was molded under about 7000 pounds pressure into smallrectangular bars about 10 cm. long, which were bluntly pointed at eachend. After drying, the bars were fired at a temperature about 10 C.above the softening temperature of the glass. At fifteen minuteintervals one of the bars was. removed from the furnace for ftestand theexpansion coeflicient was measuredby means of the well known dilatometermethod. Fifteen minutes sufilced to sinter the powdered glass andconvert the pulverulent material to a vitreous non-porous glass bodyprovided the powdered glass did not devitrify. The tendency-for theglasses to devitrii'y increased as the heating was prolonged. .Someglasses devitrified badly in fifteen minutes. For most glasses, theexpansion coefiicient following. a fifteen minute heating was increasedat least slightly while in extreme cases the expansion coefllcient wasdoubled or tripled in the same length of time; :Glasses, in which thereis no change or expansion coeflicient after fifteen minutes 'sinteringor in which the change of expansion coeillcient from that of theoriginal glass amounts to not over 5x10 per degree (3., are suitable formy purpose.

The following compositions which were calcu lated from their respectivebatches in percent by we ar m es of l s es r n-ms within Table I 77.5 8077.6 70 79 74 81 80 O 10 10 6 2.5 10 2.5 5 Oz. 12.5 10 17.5 15 18.5 1515.5 11 A O- 1 1 4 Slnter Temp.

"C 862 862 884 813 827 844 818 915 925 Exp.X10' of original glass. 24 5161 33 66 28 49 27 35 Exp. after 15 m utes at sinter temp.-- 29 55 54 3567 28 60 29 36 Table II 72.5 70 71 77 76 4 5 10 10 2.5 5 22.5 19 15 18.513 1 4 2 v 6 Sinter Temp.,C 813 774 735 764 739 746 795 823 Exp.Xl0- oforiginal glass 28 36 72 36 67 57 42 40 Exp. after 15 minutes ats1nteitemp 30 39 76 36 67 57 42 40 The compositions shown in Table Icontain potash as the alkali metal oxide and the compositions of TableII contain soda. noted that some of the compositions contain A1203. Ihave found that although the range of suitable compositions is smallerin the soda borosilicate system thanit is in the potash borosilicatesystem, the addition of A1203 in amounts up to 6% or $0130 the sodasystem enlarges or extends its range 'of useful glasses to substantiallyequal that of the potash system. A120: can also, if desired, be, addedto the potash glasses with some advantage. tendency oiv the glass toundergo a change in expansion coeificient when powdered and, sintered.All glasses which are melted in aluminous refractories will containdissolved alumina which may amount to a tenth percent or more.

It will be In all cases it decreases the 4 the right of the line BC thevalue of this ratio is less than 1.1.

Fig. 2 is a triaxial diagram representing the systemSi02+Al202:Na20:B20s and showing compositions in this system which aresuitable for use in the practice of my invention. The area enclosed bythe straight lines MS, MN and N0 and the curved line 08 representsapproximately the compositions in the soda borosilicate system withoutsubstantial A1202 which I have found useful for my purpose. Ashereinbefore pointed out, the addition of A1202 to this system ofglasses extends the range of useful compositions. This improvement hasbeen shown in Fig. 2 for glasses containing 1% and 6% A1203. Theaddition of 1% A120: to these glasses extends the field to include alsothe area bounded by the curved lines In order that the invention maymore readily be understood, reference is had to the accompanyingdrawings in which Fig. 1 is a triaxial diagram representing the systemSi02+Al203:K20:B203 and showing compositionsin this system which aresuitable for use in the practice of my invention. These are defined bythe area enclosed by the straight lines AD, AB and BC, and the curvedline CD. The compositions which are set forth above in Table I fallwithin this area. The maximum S102 content for suitable glasses in thissystem is not constant, as is indicated by the curved line CD. Thestraight line CE is, therefore, employed as the closest approximation tothe average upper limit for $102 in order to facilitate defining thefield of useful glasses. On this basis, it will be seen that the usefulglasses in this system contain from 60% to 83% S102. The points A and Bindicate that the K20 contents of these glasses are from 1% to 21% andthe points A and 0 place the limits of B203 from 8% to 39%. Ashereinbefore pointed out, if desired, A1203 may be pres ent in amountsup to 6% or so.

The straight line BC, if extended, would pass through the Si02+Al202apex and the point on the K20, B203 axis representing 52.4% K20, 47 .6B203. This line therefore represents a constant ratio for i&0/B20a. Inthe present instance this ratio is 1.1 and for all compositions locatedto 0S and OPS. The further addition of A1202 up to 6% or sofurther'extends the field to include thearea bounded by the curved linesPS and PBS. For convenience, the straight line RT may be used as anapproximation of the curved line RS for defining the average maximumsilica content of the glasses of this system. The compositions of Table11 fall within the area thus described. r Itwill be noted that the areaMNRT is identical with'area ABCE of Fig. 1. Using the same method ofdefinition, the areaLMINRT is therefore defined as comprising from 66%to 83% SiOz, from 0 to 6% A1203, from 1% to 21% Na20 and from 8% to 39%B203.

The straight line NOPR, if extended, would pass through the Si02+Al203apex and the point on the Na20, B203 axis representing 52.4% Na20, 47.6%

B203. This line, therefore, represents a constant ratio for Na20/B203.All compositions which are located on the line ',NOPR have the ratioNa20/B20z equals 1.1 and for all compositions which are located to theright of the line NOPR the value of this ratio is less than 1.1. I Theabove described glass compositions, when powdered, molded and sinteredmay be fabricated into a variety of shaped glass articles which arenon-porous,v vitreous bodieshaving accurately contoured perforations,reticulations and the like. Compositions which lie outside of thedescribed ranges tend to crystallize when so treated and their expansioncoefficients are increased to such an extent that they are relativelyuseless for the intended purpose.

Fig. 3 further illustrates my invention and shows by way of example aside elevation of a coil form'made thereby and comprising a tubularglass cylinder It! provided on its exterior surface with ahelical wirereceiving groove H and anchor holes 12.

Fig. 4 is a plan viewof a sintered glass base Fig. 7 is a sectional viewon the line 'I! of Fi 6. v

Fig.8 is a, sectional view .on the line 8-.'8'of Fig. 7.

Fig. 9 is a plan view of a bushing for insulating a bolt in a,transformer.

Fig. is a sectional view on the line Ill-l0 of Fig. 9, which shows thatthe bushing is provided with a square recess I! for receiving the headof the bolt and a central hole 18 to give passage to the bolt itself.

Fig. 11 is a side elevation, partly in section, of a bushing forinsulating a wire. The bushing comprises a small hollow cylinder ofsintered glass one end being provided with an outer bevel IS, the otherend being provided with an inner bevel 20. Such bushings may be used incoaxial cables and the like.

A suitable procedure for making reticulated glass articles according tomy invention is as follows. The glass is pulverized and ground,preferably in a. ball mill using silica or porcelain balls until atleast 50% of it Will pass through a 200 mesh screen. To the powderedglass is added a solution or liquid comprising an organic binderamounting to about .5% to 2% by weight of the glass and the solventbeing sufficient to dampen the glass powder and wet the particlesthereof or equivalent to about cc. per 100 grams of glass. Gelatindissolved in water or cellulose nitrate dissolved in amyl acetate arepreferred as binders, but others may be used.

The thoroughly dampened batch is permitted to dry somewhat until it willcohere when pressed, but will not adhere to the mold or plunger. In thiscondition it appears dry but is definitely coherent. If water was usedas the solvent, the residual moisture at this stage will amount to about25% to 1.5% by weight of the glass. The batch is pressed in a mold ofthe desired configuration, preferably under a pressure of about two tonsper square inch.

The pressed article is then dried and heated at a, temperature near thesoftening point of the glass, preferably within i25 to 50 C. of thesoftening point until the particles are fused together to form asubstantially continuous glassy structure. A heating time of not morethan fifteen minutes will usually suffice.

I claim:

1. A shaped glass article having accurately contoured perforations,reticulations and the like formed by compressing into the desired shapea finely pulverized glass falling within the composition range 60% to83% S102, 0 to 6% A1203, 1 to 21% R20, and 8% to 39% B203, the ratioR/B20a being less than 1.1 and sintering the shape into a densenon-porous article, the coefficient of expansion of the sintered articlenot exceeding the coeflicient of expansion of the glass beforepulverizing and sintering by more than .0000005 per C.

2. A shaped glass article having accurately contoured perforations,reticulations and the like formed by compressing into the desired shapea finely pulverized glass falling within the composition range to 83%S102, 0 to 6% A1203, 1 to 21% K20, and 8% to 39 B203, the ratio K20/B203being less than 1.1 and sintering the shape into a dense non-porousarticle, the coeflicient of expansion of the sintered article notexceeding the coefilcient of expansion of the glass before pulverizingand sintering by more than .0000005 per C.

3. A shaped glass article having accurately contoured perforations,reticulations and the like formed by compressing into the desired shapea finely pulverized glass falling within the composition range 60% to83% $102, 0 to 6% A1203, 1% to 21% Na20, and 8% to 39% B203, the ratioNa20/B203 being less than 1.1 and sintering the shape into a densenon-porous article, the coefllcient of expansion of the sintered articlenot exceeding the coefiicient of expansion of the glass beforepulverizing and sintering by more than .0000005 per C.

4. The method of making glass articles which comprises preparing afinely pulverized glass the composition of which lies within the range60% to 83% Si02, 0 to 6% A1203, 1% to 21% R20, and 8% to 39% B203, theratio R20/B203 being less than 1.1, forming the pulverized glass intothe desired shape and sintering it into a dense nonporous article.

HARRISON P. HOOD.

REFERENCES CITED The following references are of record in the

